Device for regulating the amplitudes and damping in sound apparatus



Get. 19 1926.,

W. HAHNEMANN DEVICE FOR REGULATING THE AMPLITUDES AND DAMPING IN SOUND APPARATUS Filed Feb. 4. 1921 Patentecl Oct. 19, 1926. 1,604,041

UNITED STATES PATENT OFF-ICE.

WALTER HAHNEMANN, O! KITZEBEB/G, NEAR KIEL, GERMANY, ASSIGNOR TO THE FIRM SIGNAL GESELLSCHAFT M. 13. BL, OF KIEL, GERMANY.

DEVICE FOR REGULATING THE AMPLITUDES AND D AMPINGIN SOUND APPARATUS.

Application filed February 4, 1921, Serial No. 442,577, and in Germany August 18, 1919.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF H'ABGH 3, 1921, 41, STAT. L, 1818.)

In the art of sending and receiving sound formation of the amplitudes are soon waves consideration must be given to the reached, especially where very rapid vibraratio of the amplitudes of motion to the amtions have to be dealt with. 65 plitudes of pressure (which varies with the A more reliable and simpler solution of degree of compressibility of the sound propthe problem can be achieved by interposing agating medium), because the amplitude of vibratory structures such as tuning forks,

the motions executed by the mechanical parts rmgs, diaphragms or the like, instead of in the sound producer or receiver proper levers, between the radiating member and the of the sound apparatus is a matter of imsound detector or producer proper, provided 10 portance. 'Assuming that a microphone 1s that these structures are arranged to exe- 'used for the reception of sound waves, it cute motions of different amplitudes at difwill be found that to obtain the maximum ferentparts of their surfaces. Structures of of responsiveness in the microphone the amthis k1nd that may be employed with parvplitudes of the motions executed by the electicular advantage are such as consist of bulky 15 trode of the microphone 'and the force at masses or weights connected by elastic con- Which they are executed have to be of a necting members of relatively little mass. certain well defined magnitude. Apart from But in employing such vibratory structures incidental cases, the absolutesizes of these it is necessary in order to obtain a certain amplitudes will never coincide with the corrat1o of transformation, to make the masses 20 responding magnitudes occurring in the formlng part of the vibratory structures sound propagating medium; and it is enthemselves of a certain Well defined size. erallynecessary,when water for examp e is Now since the absolute sizes of the masses the propagating medium, to transform the used in the vibratory structures determines very small amplitudes of motion' having the damping of these structures and of the 25 very great force that it executes into larger radiating members of the sound apparatus, amplitudes having less force before applying it follows that if the transformation of the the vibrations to the sound-receiving microamplitudes is produced .by the vibratory phone. If the propagating medium is air structures alone, then a given ratio of transthe amplitudes will be very large and hence formation will always also imply a certain so these will have to be transformed down, indamping whose magnitude can only vary stead of up as in the case of water, before within very narrow limits. they reach the ,microphone. Similarly, in It is to this particular point that the pressending out sound through water the amplient invention more particularly relates. It

tudes of motion executed by the members of consists in obtaining the transformation of the sound producer proper (the electromagthe amplitudes by interposing. a combinanet or the like). will of necessity be larger tion of levers and vibratory structures be than those executed by the sound radiating tween the radiating member and the actual body abutting on the water, while here sound producing or receiving (detecting) again the opposite is true if it is a question .member of the sound signalling apparatus 40 of sending out sound into the air. by which sound waves are sent out or re- In order to effect this augmentation or ceived through .any propagating medium. diminution of the amplitudes of the sound' This renders it possible to select masses for vibrations on their passage from the radiatthe vibratory structures whose sizes may ing member to the sound detector, or from vary between very wide limits, because now 45 the sound producer to the radiating member, an additional means for regulating and comlevers or similar devices have been employed pleting the desired ratio of transformation which are inserted between the. saiduparts is at hand in the shape of the lever. Thus and so arranged as to transform the amplithe relative freedom with which the masses 10o tudes u or down as desired. But in putmay be selected renders it possible to make 50 ting the idea into practice the limits of the damping of the vibratory structure, as engineering desi in regard to the construcwell as that of the radiating member, of tion of reliable evers for an eflicient trans any desired magnitude, and one is even able,

' phragm 1, which closes a casing 2.

in the case of sound receivers for instance, to make the useful damping larger than the damping of radiation. In electromagnetic sound producers and receivers constructed according to the invention, the additional advantage is obtained that the quantity of iron required, and hence the losses of energy in the iron, can be considerably reduced.

Some constructional forms of the invention are shown in the drawing, partly diagrammatically.

Fig. 1 shows an electromagnetic sound apparatus suitable for use as a producer and receiver of sound waves in water and equipped with a lever and an electromag netic device in the shape of a vibratory structure.

Fig. 2 shows a similar apparatus with a difi'erently arranged lever and an electromagnetic vibratory structure provided with an elastic member that is subjected to longitudinal stresses.

Fig. 3 shows a microphonic receiver for water sound waves,- the microphone being constructed in the form of a special vibratory structure.

Fig. 4 represents a microphonic receiver for air sound waves having a vibratory structure in the form of a rod or bar and having microphones attached to this structure.

In the apparatus shown in Fig. 1 a short portion of a lever 3 is attached by a flexible connecting member 4 to the centre of a dia- The fulcrum of the lever is a flexible member 5 by which the lever is attached to the wall of the casing, and its free end carries a magnetic device which is adapted to operate as a vibratory structure. The magnetic device comprises the magnetized iron 6 and the armature 7, which are connected to each other by an elastic diaphragm 8. The magnetic device has a coil 9 embedded in the iron and adapted to carry the current produced in receiving sounds.

When receiving, the sound waves impinging on the diaphragm cause it to vibrate and to move the lever 3 which transfers the vibrations to the electromagnetic device. The lever, when receiving, is a lever of the third class, with the fulcrum at 5, the power at 4, and the weight at the end attached to the vibratory structure. The mechanical advantage derived from such a lever is an increase of travel of the weight. The action of the particular lever shown is such that it reproduces on an enlarged scale at its.

weight end the amplitudes of the motions executed by the dlaphra at the point where this latter is attac ed to the lever. The free or unrestrained mass 7 of the vibratory structure (electromagnetic device) is made smaller than the mass 6 attached to the lever, so that a second transformation brating masses connected by an elastic member, such as shown, are inversely proportional to the magnitudes of the masses. When the apparatus is used for sending instead of receiving, the amplitudes of motion will be transformed down, instead of up, in a corresponding degree. In this case the lever becomes a lever of the second class, with the'weight at 4, the fulcrum at 5, and the power at the other end. The amplitudes of the forces exercised will always be transformed in the opposite sense to that of the motions.

In Fig. 2 the lever is made in the form of an auxiliary or secondary diaphragm 13 which is connected to the primary or sealing diaphragm 1 of the casing 2 by means of a forked rigid member 10 whose points of attachment 11 with the diaphragm shaped lever 13 are flexible in all lateral'directions. When sending, the diaphragm 13 forms a lever of the second class with the fulcrum at 12, the power at 5, and the weight at 11; whereas, when receiving, the diaphragm becomes a lever of the third class with the fulcrum at 12, the power at 11, and the weight at 5. The diaphragm-shaped lever 13 is provided with radial stiffening ribs 14 and it is attached at the centre to the separate vibratory structure that consists of the magnetized iron 6 and an armature 7 which are interconnected by an elastic connecting member 8 This latter is constructed of a rod and a concentric tube. Attached to the free end of the tube is the armature 7 while the adjacent end of the rod is fixed to the iron of the electromagnet. At their farthest points from the magnet the rod'and the tube are attached to each other. As in the case of Figure 1, the freely vibrating mass 7 is smaller than the mass 6, so that the amplitude of vibration of mass 7 is greater than that of mass 6; for this reason the vibratory structure or system changes the amplitude of vibrations passing through it. The whole system vibrates in such a manner that the elastic connecting member is alternately stretched and contracted in the direction of its length. As far as the production or reception of sound is concerned, the apparatus operates in the same manner as the apparatus of/ Fig. 1.

The receiving apparatus of Fig.3 is constructed, as far as the actual receiving device and the lever arrangement is concerned, 1n precisely the same way as the apparatus of ig. 2. Hence like parts in hot figures are marked by like signs of reference. But in Fig. 3 the vibratory structure is constructed in the form of a microphone in which the electrodes 15 and 16 are. arranged to act as vibrating masses that are mechanically interconnected by an elastic diaphragm-l'f. Here also the mass 15, attached to the diaphragm-shaped lever (the mass inthe purposes of submarine or subaqueous signalling. The numeral 21 designates the granulated carbon between the electrodes 15 and 16, which carbon is retained in placeby the ring 22 of felt or the like.

The apparatus shown in Fig. 4 is intended to act as a receiver of air sound waves. It dilfers vfundamentally from the-preceding apparatus in that the amplitudes of motion are transformed down in the direction from the outside or sealing diaphragm towards the microphones 18, 19. This apparatus al so differs from the others in that its sealing or wave collecting diaphragm itself is arranged to act as an amplitude-transforming lever. Here the lever is a lever of the second class. The point of attachmentof the separate vibratory structure, which in this case takes the form of a simple strai ht bar 20, is not located at the middle of t e diaphragm where the diaphragm oscillates farthest, but at oints that execute a smaller travel or amp 'tude.- To make certain that the diaphragm will execute vibrations of the form desired, it is equipped with ribs 14. The connection between the diaphragm and the bar 20 is made by means of a rigid intermediate member or members 10 of the aforementioned kindl The bar 20 is attached to the member 10 in such a manner that the former executes its largest travel at the point of attachment. At its outer free ends the bar carries weights so that its nodal points are shifted near to its ends, and attached to the said weights are microphones 18. 19.

The arrangement of the levers and separate vibratory bodies or structures may be such that they pass through each other, as it were. Thus the masses of a vibratory structure, in addition to being connected to each other by elastic members, may also be interconnected by levers or bodies that act as such, so that a combination of a lever and a vibratory structure is obtained in a single device.

The scope of the practical applicability of the invention is not limited to the constructional formsshown in the drawings and described in the preceding paragraphs. By combining the ldeas revealed in the same in constructing novel apparatus, and by the addition of known elements, as by employing other kinds of levers or vibrator structures, any desired variations may produced. The ratio of the transformation of the amplitudes "is not limited in anyfizvay 813d soun only depends upon the nature of propagating medium and upon the character of the sound-producing or detecting principle employed. The invention is important for continuously and non-continuously excited sound producers actuated in any desired manner and also for receiving apparatus with electric contact detectors, or detectors of any other type. Finally it will be said that the fact that in all of the illuse trated constructional forms the levers are shown next to the diaphragm and the vibratory structures are then attached to the levers, is not to be construed to mean that the order of the arrangement may not be the opposite, for as far as the order of the elements and the number of the vibratory structures. and levers is concerned, any desired combination is possible.

It is well known that the receiver (detector) or sound producer proper of a sound signalling apparatus is a device which converts one form of energy, such as electrical or mechanical energy, into another, such as sound energy, and that the diaphragm or wall or vibrating body abutting on the medium (water or air) through which the sound waves are propagated, radiates sound waves not only in a sound producing appa ratus but also in" a sound receiver. Hence the receiver or sound producer proper may be properly called an energy converting de vice and the said diaphragm or vibrating body may in all cases be called a sound radiating means. These terms will be adopted for the sake of brevity in the following claims.

I claim:

1. In a sound apparatus, comprising in combination, two systems of transformation of vibration amplitudes, a sound radiating diaphragm, a lever stem for transforming the vibration obtained at the sound radiating diaphragm to a desired amount, a second.

transformation structure comprising two substantial unequal masses connected by a substantially massless elastic member for completing the desired amplitude transformation, one of said masses being positioned at a chosen point on the lever system.

2. A sound apparatus comprising a vibratory system for amplifying motion formed of two unequal masses coupled by an elastic member, means for energizing said vibratory system, said means associated with said masses, a lever structure, one of said masses operating at one'point of said lever structure, a sound radiating member, said radiating member operating at another point of said lever structure whereby the motion of said last mass is further transformed at the sound radiating member.

In testimony whereof I have aflixed my signature.

WALTER HAHNEMAN N. 

